19).
[Illustration: Fig. 19.--Erect Tree containing Reptilian remains.
Coal-measures, Nova Scotia. (After Dawson.)
In many cases fossils enable us to come to important conclusions
as to the climate of the period in which they lived but only a
few instances of this can be here adduced. As fossils in the
majority of instances are the remains of marine animals, it is
mostly the temperature of the sea which can alone be determined
in this way; and it is important to remember that, owing to the
existence of heated currents, the marine climate of a given area
does not necessarily imply a correspondingly warm climate in
the neighbouring land. Land-climates can only be determined by
the remains of land-animals or land-plants, and these are
comparatively rare as fossils. It is also important to remember
that all conclusions on this head are really based upon the present
distribution of animal and vegetable life on the globe, and are
therefore liable to be vitiated by the following considerations:--
a. Most fossils are extinct, and it is not certain that the
habits and requirements of any extinct animal were exactly similar
to those of its nearest living relative.
b. When we get very far back in time, we meet with groups of
organisms so unlike anything we know at the present day as to
render all conjectures as to climate founded upon their supposed
habits more or less uncertain and unsafe.
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